Could also be a delayed carb flu. From what I've read here, sometimes carb flu kicks in right about three weeks.
If it IS carb flu, don't worry, it will be gone in two weeks and you'll have a LOT of energy for P90x2. Hang in there and DON'T increase the carbs yet. If you don't feel more energy in 10 days or so, then yes you probably need a few more carbs.
5'0" female, 42 years old.
Started Primal October 31, 2011, at a skinny fat 111.5 lbs.
Current weight: 101.5. lbs and holding steady. Spring yardwork here we come!
Co-worker 1: Needs to lose ~50. Now he wants to start Mayo Clinic Diet. Yeesh. Give it up, man.
Co-worker 2: Needed to lose ~55. Lost 20 from stress. Started Primal in Sept, lost 20 more, but gained 10 back on a carb spree. We're working on it.